AutoCad :: How To Make Third Line Relative To Second Line So Angle Is 75 Degrees And A Certain Length

I have been practicing using a older book(copyright 1990) and it has some decent exercises in it. I was able to do this one but it seems I can"t find the proper way to do this..First drawing a line a certain distance..ortho on,click the first point anywhere,move curser to the left and click again. that gives me a line at 180 degrees at what ever length..Line command again starting at the second point of the first line..after clicking that point,I type in @2.38<150 that gives me a line2.38 long at 150 degrees..now how do i make a third line relative to the second line so that the angle is 75 degrees and a certain length..the picture shows what I am trying to draw..using the polar cordinates you get an angle based off the UCS( which is set at world) when you try to draw the third line ..that makes the angle between line 2 an 3 not the angle that I want..To make the drawing,I rotated the ucs -30 degrees..But there has to be a better way than that..